This invention relates to the joining of tubes to other components in fluid systems. More specifically, this invention relates to gas impermeable tube joints and methods for forming gas impermeable tube joints in fluid systems.
In general, fluid systems serve to contain a fluid (e.g., a liquid, vapor, gas) as it is transported from one location to another. Fluid systems typically include a number of components interconnected by one or more tubes, which transport the fluid between the components. The components and tubes are connected together by joints, which allow the fluid to flow between the components and tubes while preventing leakage of the fluid from the system.
For certain fluid systems, it is important to prevent the infiltration or escape of the fluid in its gaseous state. One such fluid system, for example, is a fuel fill system in a motor vehicle, through which fuel is delivered to a storage tank. The escape of fuel vapor from fuel fill systems can be hazardous to the environment, and as a result, the U.S. Environmental Protection Agency prescribes limits to the amount of fuel vapor that may escape from the filler pipe. Another example of such a fluid system, is a radiant heating system found in homes and businesses. Often times hoses in a radiant heating system supply water or other heating fluid to heat exchangers located in floors, ceilings, roofs, and concrete or asphalt slabs. The hoses may be embedded in the surfaces to be heated. A significant problem with such hoses is that they are subject to gas infiltration and exfiltration. Oxygen is particularly troublesome because it is able to penetrate all known plastic films, at least to some small degree. Once oxygen has gained entry to such a heating system, it deteriorates the hoses and corrodes the pumping system. These are only a few examples of systems requiring gas impermeable tube joints and there are myriad fluid systems for which the prevention of the infiltration or escape of gas is critical to operation.
One way to reduce the infiltration or escape of gas in a fluid system is through the use of tubes having metallic barrier layers. For example, U.S. Pat. No. 6,074,717 to Little et al., describes a flexible hose that has an aluminum barrier layer for preventing ingestion of oxygen and other gasses. The aluminum barrier layer is securely bonded between two adhesion tubes which are vulcanized in place against the aluminum. The resulting tube is flexible and substantially gas impermeable. While such tubing is sufficiently gas impermeable to prevent the permeation of gas along the tube, the joints between tubes and components remain an area where the infiltration or escape of gas can occur.
Typically, the joints in such fluid systems are formed by sliding the tube over a projection on the component, and securing the tube in-place by way of a barb formed on the projection and/or a mechanical fastener (e.g., a hose clamp). Problematically, this method may allow for the permeation of gas through the joint connection. If the tube has a metallic layer, the permeation may be worse because of the relative inflexibility of the tube material and the resulting inability of the tube to form a tight fit with the projection.
Thus, there is a need for gas impermeable tube joints and methods for forming gas impermeable tube joints in fluid systems.